1. Field of the Invention
The present invention relates to a damper for absorbing an impact, and more particular to a damper suitable for use in a vehicle seat having a headrest for supporting the head of a seated person by moving forward when, at the time of such as a collision of a vehicle, the seated person moves backward due to inertia upon receiving an impact from the rear, as well as a vehicle seat equipped with the damper.
2. Description of the Related Art    Patent Document 1: JP-A-10-181403    Patent Document 2: JP-A-10-119619    Patent Document 3: JP-A-11-268566    Patent Document 4: JP-A-2003-81044    Patent Document 5: JP-A-2003-176844    Patent Document 6: JP-A-2005-225334    Patent Document 7: JP-A-2006-82772    Patent Document 8: JP-A-2006-88875
In vehicles, vehicle seats have been proposed in which a headrest is adapted to move forward to restrict the head of a seated person at the time of such as a collision.
Shock absorbing dampers which are used in such vehicle seats are required to be such that, in the collision at the time of low speed, the impact caused by the collision is absorbed softly in order to support the head so as not to impart the impact, whereas, in the collision at the time of high speed, the impact is absorbed with stiffness corresponding to the magnitude of the impact at the time of the collision so as to absorb the impact due to the collision by becoming stiff in order to support the head reliably.